1. Technical Field
Example embodiments of the present invention relate in general to a device-to-device communication method, and more particularly, to a method for improving flexibility of radio resource management for device-to-device communication.
2. Related Art
Device-to-device communication (hereinafter, also referred to as D2D communication) means a communication scheme in which data communication between adjacent two terminals is directly performed without intervention of a base station. That is, the two terminals become a source and a destination to communicate with each other.
Regarding a use case in which device-to-device communication may be efficiently used, various discussions have been carried on. As an example, device-to-device communication may be used for a local media server that provides mass data (e.g. rock concert program and musician information) to visitors to a rock concert.
Here, each device may access a serving cell to perform a telephone call or internet access by using a conventional cellular link, and may also directly transmit/receive the mass data to/from the local media server acting as a counterpart of D2D communication.
A D2D link is not only enabled among devices having the same cell as a serving cell, but also enabled among devices having different cells as serving cells. For instance, device 3 belonging to a first base station may communicate with device 6 belonging to a second base station.
Device-to-device communication may be classified into centralized D2D communication and distributed D2D communication.
According to centralized D2D communication, a device desiring communication with another device asks a central node (base station in a cellular node) that performs control to set up a link, and the central node allocates, when the counterpart device is located near the device, radio resources so that the devices communicate with each other. Here, almost all operations of the devices are managed by the central node, and radio resources allocated for the cellular link or another D2D link may be reused for D2D communication.
According to distributed D2D communication, a link is set up in a distributed control manner through direct signal exchange between devices without depending on a single central control node, and, by using this link, data is directly exchanged with an adjacent device. FlashLinQ technology proposed by Qualcomm Incorporated is a representative distributed D2D communication technology. FlashLinQ technology corresponds to synchronous technology based on time division duplexing (TDD).
According to current distributed D2D communication technology such as FlashLinQ technology, each D2D link is scheduled in the whole frequency band to perform data transmission between devices. Therefore, a communication range is reduced, and it is difficult to accommodate a low-power device. Further, in order to increase granularity of resources, signaling overhead for connection scheduling or rate scheduling is increased.